Vacuum electric tube device



July 9, 1929.

E. Y. ROBINSON VACUUM ELECTRIC TUBE DEVICE Filed Q 1924 ZSheets-Sheet lmylor Ewefs'f )25/710 ZZZ/mm y 11? 192202774 July 9, 1929, E. Y. ROBINSON VACUUM ELECTRIC TUBE DEVICE Filed Nov. 26, 1924 2 Sheets-Sheet 2 Patented July 9, 1929.

UNITED STATES Parser err-res.

ERNEST YEOMAN ROBINSON, OF WITHING-TON, MANCHESTER, ENGLAND, ASSIGNOR TO ASSOCIATED ELECTRICAL INDUSTRIES LIMITED, A BRITISH COMPANY.

VACUUM ELECTRIC TUBE DEVICE.

Application filed November 26, 1924, Serial No. 752,480, and in Great Britain llecember 18, 1923.

This invention relates to vacuum electric tube devices and provides an improved construi'ztion and mounting of the electrodes oil such devices. The im ention more especially but not exclusively concerns the electrodes oi? such. tubes wluucinv the inter-electrode gap is small, the object being a construction in which the elt-zctrodes are registered and maintained. registered or accurately and. rigidly disposed. with respect to one another.

In vacuum electric tubes as heretofore commonly coi'istructed wherein the elec trodes are of tubular :liormation, the grid commises a number of turns of wire and welded, lashed or otherwise attached along its lei th to a si'ipporting stem. ll or example to stem may consist of a wire which is bent so as to have two parallel and adja-.

cent arms between which the convolutions Ofli a helical grid are clamped.

In. such a ci'mstrliction, although individual turns or conwilutions oi: the grid helix are selil -supporting in themselves, the whole helix is not solf-supporting, but is flexible. l'V ith such a constrruition. it is not possible to register the grid helix or convolutions accmiately with regard to the grid su nport, to which they are welded or lashed, and the grid is theretlore unsuitable for use in. a valve wherein. the inter-electrode gap small hecruse ol? the lack oi? registering means. ing is the only method by which the grid. helix may be secured to the support in accm'ato and, prodetermined relation thereto. However, with such. constructions even when the grid helix is secured to the support by welding accurate registration thereto cauuot he obtained when. the grid wire line. This is because it the grid wire is of nickel or the like, it is distorted during welding and. moreover each individual. turn of the grid helix is not su'lliciently strong to prevent movement due to handling or to its own weight when it is heated in the valve. On. the other hand, if the grid is of tungsten, for example, which i'i'lalcrial. very still at room temperature and is still strong at high temperatures it is not possible to weld it easily to a support without distortion and even when it is so welded the weldis not sulliciently strong to act both as a means for seciui'ing the helix to the support and to register the helix to the support. In other in such known constructions welds forms oil? tubes the grid. elcctrtiules have been constructed of metal. frames having grid wire wound thereon, but in. such. case the individual turns of the grid. are not self-supporting and the grid wires are in. effect suspended across the metal supporting frame.

lluccordiu g to the present ijuvei'iti on a tubular grid of wire in. coil, mesh or other openwork formation is secured to a rigid support which. presents at least two lines 01' con tact to the turns or meshes of the wire grid proper substantially throughout the length of the latter. In this manner a wire grid which. is necessarily of a flexible natlufe is rendered comparatively rigid and can. be rtaulily minstraiued or registered to occupy a predetermined position with respect to other electrodes since the wire gridis delinil'ely and accurately registered with respect to the grid support, which in turn can be constrained or registered with respect to the other electrodes in a suitable manner. Thus the grid may be accurately and positively located in. the small. gap between. a filamentary cathode and a tubular anode closely spaced lllltlltillUTl].

The grid wire may be secured to the support in various ways such as by welding or lar-dung. la the case where the support presents more than two lines oi? contact to the grid proper separate means for secur iug the wire grid tube thereto may he cispeused with. it: it Hi arran ed that at least three lines oil contact are tlormod which. are so spaced around the grid tube that the latter is held thereby but even in this case ad.- ditional setalriug means may he used, at the ends of the. grid tube for example. its poii'itcd out above the grid. is accurately registered with res1 )ect to the sup} iort and may be mounted. in position with It rence to the other electrodes by means 5 the sup port. However, the grid itself when it consists of tui'igstcn is so rigid and. strong that it may be held in a-jig with the other electrodes and positioned. therein by a wire or tube passing downv the grid helix while the electrode supports of: the valves are pinched. into glass serving as a spacing medium.

The supports are conveniently in the form of V-blocks which are of substantially the same length as the wire grid tube, or in. some cases slightly longer to provide registering portions.

The form of the support and the mount ing thereof may vary with the nature and form of the other electrodes of the vacuum tube. Tov enable the invention to be clearly understood several arrangements will now be described by way of example with reference to the accompanying drawings in which,

Fig. 1 is a perspective view oi a simple form of the improved grid in accordance with the invention, and Fig. 2 an end view thereof. Figs. 3 and I are sections of modified forms of the support for the grid helix. Figs. 5 and 6 are respectively a plan view and a transverse section of another form of grid in accordance with the invention. Figs. 7 and 8 are detail views of a grid structure suitable for a'valve having a twin filament, and F ig. 9 is a perspective view of the complete grid structure. Figs. 10 and 11 are respectively a front elevation, and a side elevation partly in section, of an electrode structure of a valve including a grid in accordance with the invention.

' Referring to Figs. 1 and 2 of the drawings, the grid therein illustrated comprises a wire helix 1 of tungsten, molybdenum or nickel for'example, tungsten being preferred since by the use of this material a rigid grid is obtained and in the case of power valves the helix is better able to withstand the high temperature which it acquires when located in close proximity to the cathode.

The wire helix 1 is mounted upon a grid support 2 which comprises a flat slab or bar of metal, for example molybdenum, having along one edge thereof a- V-groove 3. The grid-helix 1 rests in the groove or against the two outer edges created by the provision of the groove 3 and is secured in position by means of binding wire at passing between the convolutions of the helix and around the slab or bar 2. Instead of a V-groove the slab or bar 2 may be provided with a groove of circular section the radius of which is substantially equal to or is slightly less than the radius or the grid helix 1. The bar 2 has a thickness of at least one-twelfth the periphery of the helix 1, as will be seen from the drawing, to insure rigidity of support of the helix. Instead of employing a solid slab or bar 2 a grid support may be employed comprising for example two strips 5 and 6 of sheet metal suitably secured together such as by stapling, welding or riveting, and having each a splayed-out edge 7 by which the groove 3 is constituted. Or shown in Fig. 4 the support may consist of a sheet or strip 8 of metal folded'at 9 around a rod 10 which may constitute a supporting stem for the grid structure, the edges being splayed out providing'the groove 3 as described in connection with Fig. 3.

. Grids constructed as above described may be supported within the valve envelope by means of stems or wires welded to the grid support or integral therewith and themselves pinched within the tent or seal ol the valve. Or as mentioned in connection with Fig. 4 the wire or rod 10 may constitute the grid, support.

As previously herein set forth the grid support may present more than two lincs oi contact to the grid wire and Figs. :1 lo fl inclusive illustrate examples of this kind. In Figs. 5 and (l the grid helix 1] is shown supported between a pair of grooved sla s or bars 2 located in a. common plane and having the grooved edges dircclcd towards one another and partially embracing the helix 1. The slabs may be connected together by means of cross strips 14 arched as at 15 so as to embrace the ends ol the grid helix 1 and secured to the slabs 2 by \vclding' or otherwise. Instead ol, the slabs 2. builtup supports such as illustrated in l i 's I; and imay be employed. Thus in l igs. 7, S and 9 two grid helices 1 of tungsten or molybdenum tor example are carried in a support comprising two metal plates it of molybdenum stamped or pressed lo the 'l'oru! clearly shown in Fig. 9, that is to say provided witl a. plurality of windows '17 and integral. arched connecting strips 19. The edges of the cut-out window portions are splaycd as indicated at ll) to provide the V-groovcs licrcinbel ore referred to. The plates 18 may be fastened together by mcaus of staples indicated at 20 or they may be welded, riveted or otherwise sccurcd (ogether.

A tubular grid of the kind illustratcd in Figs. 1 and 2 may be supported along with the other electrodes ol. the. tube in th itoh lowing manner.

Referring to the construction illustrated in Figs. 10 and 1]. the grid is oi the type illustrated in Figs. 1 and 2 except that the support 2 is provided with slots 39 by means of which the grid is rcgislcrcd in position with rcilcreinfie to the other electrodes which are mounted upon a frameworlr which is generally of similar general construction to that illuslratcd and scribed in my copcnding application Scrial No.'722,8l1 filed June 27, lfliZ-l. Thcrc arc two such grids which co-opcralc with two anodes 10, each anode being prctcrably formed 0.1? molybdenum sheet. The lilaments are supported and registered in the manner described in. the specification ol my copending application, Serial No. 717,327. filed 2nd June, 1924'. At their lead-in ends the filaments are supported by means of supports 14. The two filaments are in a plane at right angles to that containing the insulating side members 26 of the framework. The upper end of the filament is constructed in the manner described in the specification of my copcndiug application, Serial No. 7455,194 filed Oct. 2 1921', the

short-circuiting strip 45 comprising a lllO lUS

molybdenum strip so shaped as to be flexible in the axial. direction of the filament, as described in the specification just above mentioned. The filament wires pass through a constraining strip 46 which is provided with end perforations through which the side members of the framework pass and small. perforations through which the tilas ments pass and are thereby registered. whilst held. in tension by means of springs 49 which engage nickel. tabs 50 attached to the upper ends of the filaments. The springs 49 are in turn secured to angle brackets of nickel 5i. welded. or otherwise attached to the upper frame member. The registering cross piece it; held in spaced, relationship from the end member 27 oi. the :i'ramework by means ott two nickel wires 52 welded re spectively to the lirame member and to the cross piece 46. The two grids are supported. on the framework by means oi two cross pieces 53, each oi. which comprises a metal plate having end perforations for the side members of the framework and other perforations adapted to receive the respective ends of the grid. supports 2 and having portions adapted to be engaged withinv the slots 39 within the ends of the grid supports 2, thereby registering and holding the grids in position upon the Framework.

The two anodes are s1'ip )orted from the framework by two cross pieces 58, each off which comprises a metal. plate having end. perforations to permit it to be mounteifl. on the side members of the fran'u-nvork and. having two inwardly extending slots of shape corresponding to the external contour oi. the anode members 410. The various cross pieces may be secured upon the vitreous side members of the framework by binding with wire. The valve describedin conncction with. Figs. 10 and 11 is of the type set :iorth in the specification. of my copend ing application, Serial No. 603,715, filed 27th November, 1922, aforesaid. The inter electrode space is small and the discharge at the ends of the filaments is confined to the inter-electrode space by reason of the fact that the ends oi the filament are cooled. Discharge through the open portions of the anodesalong the length of the filaments is prevented by reason of the presence of the grid supports 2 which being comparatively thick exert both an electrostatic and a mechanical screening effect upon the discharge. The anode lead-in wire 63 is connected to the two anode cross pieces 58 whilst the lead-in wire (i l. for the grid is connected to the two grid cross pieces 53.

It will be understood that various modifications may be made without departing from the scope of the invention.

I claim as 1nyinvention:-

1. For a. vacuum electric tube, a grid structure eonnorising an openwork tube formed of wire, a bar having a channel edge which receives and partially embraces the exterior 01". said tube grid, and means for firmly holding said tube grid in engagement in said channel edge.

2. For a vacuum electric tube, a grid structure comprising an openwork tube iormcd oi? wire, a supporting member there for in. the iiorm of a bar consisting of two thicknesses of sheet metal splayed out along one edge to form a channel, and means whereby said tube grid is held in firm engagenu-mt in said channel.

For a vacuum electric tube, a grid structure comprising an opeuwork tube formed of wire, a supporting member therefor in the form of a bar consisting of a strip of metal :ifolded symnietrically about itself, a supporting rod enclosed in the fold oi? said -folded strip, the free edges oi? the iiolded strip being splayed out to form a channel, and means whereby said tube grid is held in firm engagement in said channel.

41-. For a vacuum electric tube, a grid structure comprising an openwork tube formed of wire, a bar having athickness of at least one twelfth the periphery of said tube grid and formed with a channel edge which engages along the exterior of the tube grid, and means for firmly holding the ex terior of said tube grid in engagen'ient in. said channel edge.

In testimony whereof I have hereunto subscribed my name this 15th day of October, 1924.

ERNEST YEOMAN ROBINSON. 

